Re: [PATCH 2/2] configs: Add generic qcom_tfa_optee_defconfig

neil.armstrong
2026-01-15T10:49:58Z

On 1/15/26 07:10, Sumit Garg wrote:
> On Wed, Jan 14, 2026 at 03:56:02PM +0100, Casey Connolly wrote:
>>
>>
>> On 09/01/2026 12:02, Sumit Garg wrote:
>>> On Thu, Jan 08, 2026 at 05:41:42PM +0100, Casey Connolly wrote:
>>>>
>>>>
>>>> On 29/12/2025 12:43, Sumit Garg wrote:
>>>>> From: Sumit Garg <sumit.garg@oss.qualcomm.com>
>>>>>
>>>>> Recently upstream TF-A/OP-TEE has started gaining support for Qcom
>>>>> platforms. RB3Gen2 being the first one and more to come. U-Boot in
>>>>> corresponding boot flow is packaged as a position independent executable.
>>>>>
>>>>> So, lets add a generic U-Boot defconfig for Qcom platforms to support
>>>>> TF-A/OP-TEE based TrustZone stack. Build command:
>>>>>
>>>>> $ make qcom_tfa_optee_defconfig
>>>>> $ make -j`nproc` DEVICE_TREE=qcom/qcs6490-rb3gen2
>>>>
>>>> This would be better suited as a config fragment rather than a new
>>>> defconfig imo.
>>>
>>> That's fine with me to add it as a config fragment.
>>>
>>>>
>>>> But more importantly, enabling OPTEE support in U-Boot doesn't imply
>>>> that it will be used, just that it's supported.
>>>
>>> There are real use-cases of OP-TEE in U-Boot for Qcom platforms like
>>> secure EFI variables based on OP-TEE secure storage. Have a look here [1].
>>>
>>> And sure there will be more such use-cases like fTPM, KASLR etc. can be
>>> supported based on OP-TEE.
>>
>> I was referring literally to the fact that CONFIG_OPTEE being enabled
>> doesn't imply that OP-TEE is running, it's faulty logic to assume that's
>> the case and add nodes to the DT.
>
> I don't disagree here as having a runtime check is always a better
> choice then a compile time config option. However, there isn't a common
> info method from properietary firmware that says if QTEE is running
> instead of OP-TEE.
>
>>
>> I just checked and there is an SMC call that tells you the UUID for the
>> trusted OS, referred to as OPTEE_SMC_CALL_GET_OS_UUID in U-Boot and
>> OPTEE_ABI_CALL_GET_OS_UUID in OP-TEE. Presumably this identifies OP-TEE
>> specifically.
>
> Also, we don't know how the QTEE will react to this OP-TEE specific SMC
> call given it's different variants running on legacy and the newer SoCs.
> So I would suggest to better gate OP-TEE presence behind a compile time
> check only.

So you say it's fine to add the optee node, and the driver will bail out if
OPTEE is not present, but it's not good to call OPTEE_SMC_CALL_GET_OS_UUID
in the fixup code to enable OPTEE only if present ?

It's literally the same, my point in https://lore.kernel.org/all/b60d5ee7-fa27-4dc1-8a09-964912ec5654@linaro.org/
was exactly that, just call OPTEE_SMC_CALL_GET_OS_UUID and add the OPTEE
node only if present _AND_ if CONFIG_OPTEE is enabled.

Move the CONFIG_OPTEE enable in a fragment and we're done, you will only
select OPTEE explicitly on desired platforms, and won't run the naughty
OPTEE_SMC_CALL_GET_OS_UUID on old crappy platforms.

Neil

>
>>
>> My suggestion would be to make this SMC call if CONFIG_OPTEE is enabled
>> in qcom_psci_fixup(), compare the UUID and add the node if it matches.
>
> That's exactly the first SMC call that U-Boot and Linux OP-TEE driver
> does to compare the UUID here [1] and bail out of the driver. I don't
> see a value of a redundant invoke in the Qcom specific platform code.
>
> [1] drivers/tee/optee/core.c:823: if (!is_optee_api(pdata->invoke_fn))
>
> -Sumit
>
>>
>>>
>>> [1] lib/efi_loader/efi_variable_tee.c
>>>
>>>>
>>>> So I think the more appropriate patch here would be to just enable
>>>> OP-TEE in qcom_defconfig (assuming the binary size isn't significantly
>>>> affected).
>>>
>>> The OP-TEE driver in U-Boot itself is probed based on DT and it's not
>>> only specific to Qcom platforms but every other platform using OP-TEE.
>>>
>>>>
>>>> Considering the other patch is based on this assumption that if OP-TEE
>>>> support is enabled then the board must be using it, a different approach
>>>> is definitely needed.
>>>
>>> Yeah that's true even with TF-A boot flow, there is possibility to boot
>>> without OP-TEE as well. However, TF-A generally doesn't provide a
>>> generic option to detect whether OP-TEE is running or not.
>>>
>>>>
>>>> When I was looking into this last year I remember discussing this same
>>>> issue from the Linux side, there is a good argument to be made that
>>>> OP-TEE support in Linux shouldn't be based on the devicetree -
>>>> particularly in the Qualcomm case where whether or not OP-TEE is used is
>>>> a simple software change, nothing to do with hardware.
>>>
>>> Sadly it's true for every other silicon vendor too. But OP-TEE support
>>> based on DT has become an ABI unless migration for OP-TEE support based
>>> on FF-A comes into picture.
>>>
>>>>
>>>> So in general I'm not particularly keen on this approach, I think it
>>>> /might/ be acceptable for U-Boot to have some fixup code to add the
>>>> OP-TEE node if OP-TEE is in use with the idea of phasing that out in
>>>> favour of runtime detection in the OS itself. I'd also expect that fixup
>>>> code to go in the generic U-Boot DT fixup code that runs before we jump
>>>> to the OS (like the EFI DT fixup function).
>>>
>>> The EFI DT fixup code is already there based on U-Boot DT. Have a look
>>> here:
>>>
>>> boot/image-fdt.c:627: fdt_ret = optee_copy_fdt_nodes(blob);
>>>
>>> In general on Arm platforms there isn't any SMC bus to detect
>>> dynamically if there is support for OP-TEE or not. That's why
>>> platform bus was choosen for the U-Boot and Linux OP-TEE driver. It's
>>> similar to how we have the SCM DT node for Qcom platforms.
>>>
>>> FF-A bus tries to solve that problem to unify that approach for future
>>> platform but U-Boot hasn't yet gained support for FF-A based OP-TEE
>>> driver too.
>>>
>>> Anyhow, this is the sanest way I can come up with to enable OP-TEE
>>> support in a general way for all the Qcom platforms. This is aligned
>>> with how OP-TEE support is detected for other silicon vendors too.
>>>
>>> -Sumit
>>>
>>>>
>>>> Kind regards,
>>>>
>>>>>
>>>>> For more information refer here:
>>>>> https://trustedfirmware-a.readthedocs.io/en/latest/plat/qti/rb3gen2.html
>>>>>
>>>>> Signed-off-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
>>>>> ---
>>>>> configs/qcom_tfa_optee_defconfig | 7 +++++++
>>>>> 1 file changed, 7 insertions(+)
>>>>> create mode 100644 configs/qcom_tfa_optee_defconfig
>>>>>
>>>>> diff --git a/configs/qcom_tfa_optee_defconfig b/configs/qcom_tfa_optee_defconfig
>>>>> new file mode 100644
>>>>> index 00000000000..c398521770f
>>>>> --- /dev/null
>>>>> +++ b/configs/qcom_tfa_optee_defconfig
>>>>> @@ -0,0 +1,7 @@
>>>>> +# Configuration for building a generic U-Boot image
>>>>> +# with support for TF-A/OP-TEE based Arm TrustZone stack.
>>>>> +
>>>>> +#include "qcom_defconfig"
>>>>> +
>>>>> +CONFIG_TEE=y
>>>>> +CONFIG_OPTEE=y
>>>>
>>>> --
>>>> // Casey (she/her)
>>>>
>>
>> --
>> // Casey (she/her)
>>